1. Field of the Invention
The invention relates to a flexible printed circuit (FPC) and electronic component assembly. The heat produced from the electronic component can be diffused from an opening in the backside of the FPC.
2. Description of the Related Art
A flexible printed circuit (FPC) board can be bent for connecting to different rigid printed circuit boards, PCBs for example, and thus are widely used in various electronic products such as cellular phones, cameras, liquid crystal displays, etc. FIG. 1 shows an example of an electronic component bonded on an FPC. As shown in FIG. 1, The FPC comprises an electric-conductive main layer 120, a first protective layer 124, and a second protective layer 112.
Copper is the most popular material for use in the main layer 120 and is etched to form the circuit. Polyimide (PI) is widely used as the material of the first protective layer 124 and second protective layer 112. These two layers are adhered on the front and back surface of the main layer 120.
The leads 102 and 104 of the electronic component 100 are soldered on the main layer 120 via tin solder 106 and 108 to make electrical connections with the FPC. Besides soldering, the tape automated bonding (TAB) technique is another method for making an electrical connection.
In order to satisfy the heat dissipation demands of some electronic components, such as CPUs, LEDs, and the like, an opening 126 is provided in the second protective layer 112. Heat is transmitted through the heat-conductive medium 110 on the opening 126 to the main layer 120. The heat-conductive medium 110 may be a thin plate with high heat-conductivity, or heat-conductive paste with silicon or silver balls therein.
With the technology development of the electronic component 100 can bear higher operating power, but it also produces more heat. The PI material is not adequate for heat-conduction. As shown in FIG. 2, an aluminum plate is sometimes used as the material of the first protective layer 224 to gain a higher heat-dissipating efficiency, however, this method results in a higher cost and reduced FPC flexibility.